Can't remember what the shear link was supposed to operate at - but it was quite a low speed.
A Vulcan was tasked to land and stream at sunny Scampton one fine day - for the benefit of some meeja luvvies filming it. Land, stream....nothing. OK, roll and have another go. Airborne.......then it decided to stream itself at about 1000ft before the shear link operated. Took ages for the thing to reach the ground again.
I belive it was the OCU CFI who was flying; we mere squadron rabble thought it was most amusing!